Woojoo is so cute in this! I wish beauty wasn't conflated with health. She is beautiful, he is beautiful, and one can be beautiful no matter their weight. Physical health, on the other hand, is a whole other set of criteria. Arguably if she is obese, she is not healthy, and it would be better for her if she were more fit (aka less prone to disease). But she shouldn't have to lose weight to make people like her. And all of this is not considering mental health.
Unfortunately, the only way I see the "perfect" (aka psychologically healthier) ending going is if no one gets exactly what they want— either they both end up at a medium (not slim or obese) body shape, or they learn like each other despite not fitting physical preferences (she becomes slim, he regains his weight). Right now, they both fit each others' preferences so that is great, but neither seems to be in a super healthy place mentally. Not yet.